stat100_sample_mt1_solution.pdf

SAMPLE STAT 100 - Midterm 1
Instructions:
1. Do not panic. It rarely helps.
2. Read all questions carefully.
3. Write your answers clearly in the spaces provided.
4. Where computations are required, you should show work.
5. Cross out any material you do not wish to have considered.
6. Correct answers with insufficient justification or accompanied by additional incorrect
statements will not receive full credit – perhaps none.
7. Write all answers on the test paper.
8. The exam has 34 total marks
Useful formula: for estimating a population proportion in a simple random sample, the margin
of error for 95% confidence is roughly equal ton .
€
Name: ____________________________________________
Student Number: ________________________________ ____________
Signature: ____________________________________________ 1. (4 points) A study was performed on the effects of distractions on studying. A room at a
university was set up with a sound system and a TV. Student volunteers who e ntered the room
were exposed to one of: (1) loud rock music, (2) soft baroque music, (3) an adventure movie on
the TV, or (4) quiet (no TV or music).
The student volunteers first took a brief pre -test. The students were placed into groups according
to scores on the pre-test: the top 4 formed the first group, the next 4 highest formed the second
group, and so on. There were 20 volunteers, so there were 5 groups. From each group, one
student was exposed to the loud rock, one to the soft baroque, one to the TV, and one to the quiet.
Every student was given some materials to read and study for an hour. At the end of the hour,
each student took a final test on the materials.
Circle your answer. To each of the followin g
a. What kind of study is this
i. Observational study
ii. Experiment
iii. Census
iv. Survey
b. What is the response variable?
i. Type of distraction
ii. Pre-test score
iii. Final test score
iv. The room
c. What purpose does the pre -test serve?
i. Used to create blocks
ii. It is the response variable
iii. It is the treatment variable
iv. It is the randomization device
d. The population for this study is:
i. Monkeys
ii. Adults
iii. Students at the same university
iv. All university students
2 2. (1 point) If a study is conducted ethically, which of the following are true? ( Choose one).
a. The researchers will not release the names of individuals who participated in the study
b. The researchers use randomization to select participants
c. The researchers use margins of error to report results
d. The researchers will not tell the participants what treatme nt they are receiving
3. (1 point) Why use a placebo in an experiment? (Choose one)
a. It helps to keep patients from getting sick
b. It helps to prevent bias by the researcher
c. It helps to keep the experiment more random
d. It helps to estimate how much response the other treatments are actually causing
4. (4 points) An advice columnist asked divorced readers, via her advice column, whether they
regretted their decision to divorce. About 30,000 responses were received, of which about 23,000
were from women. Nearly 75% of respondents said that the y were glad that they divorced.
a. What type of survey is this?
Voluntary response survey
b. Briefly explain why this survey is likely to be biased.
There are many good answers.
For example, people who are motivated typically will reply to voluntary surveys. Thus
those who are really happy to be divorced may have written in a response.
Could also say that had 75 % women and maybe men are more/less happy than women.
5. (2 points) A university has 10,000 undergraduate and 5,000 graduate students. A survey of the
students’ opinions is conducted by randomly selecting 100 of the 10,000 undergraduate students
and also 50 of the 5,000 graduate students. Very briefly explain why this is not a simple random
sample.
A simple random sample requires that eac h sample of size n has the same probability of being
selected. In this question, it is impossible to get a sample of, say, 150 undergraduates.
3 6. (14 points) In a 2007 opinion poll to investigate the attitudes of Americans towards stem cell
research, the following question was asked:
Do you support embryonic stem cell research?
For this study, a simple random sample of 1047 American adults was taken and 527 of the
respondents answered Yes to this question.
2 points each
a. What was the population for